Ecdysteroid hormones are key regulators of development and reproduction in the mosquitoes, Aedes aegypti and Anopheles gambiae. The proposed research will focus on the molecular characterization and expression of two types of peptide hormones involved in the activation of ecdysteroid hormone production in females of these species. First, the secretion of ovary ecdysteroidogenic hormone (OEM) and insulin-like peptides (ILPs) will be characterized. Second, their receptors and signalling pathways will be delineated. Third, activation of ecdysteroid biosynthesis by peptide hormones provides an experimental approach to identify .new proteins and their genes specifically involved in this essential process, which is incompletely known for insects. Indeed, the mosquito ovary is an exceptionally robust model for such discoveries. Peptide-treated and control ovaries will be compared by proteomic analysis to reveal translational and post- translational changes in particular proteins that then will be identified in genome databases. In addition, suppressive subtractive hybridization of cDNAs from experimental ovaries will be used to obtain a cDNA library that will be examined for novel and known gene products transcribed in response to peptide hormone activation of ecdysteroid biosynthesis. Candidate genes and proteins then will be subjected to quantitative PCR and immunoassays, and to RNA interference knockdown in vivo and in bioassays to substantiate the observed changes. The proposed work has practical import for public health in that the identification of mosquito-specific enzymes involved in ecdysteroid biosynthesis may provide targets for novel substrate poisons. As well, knowledge of peptide hormones and their receptors may allow design of bioactive, stable peptide mimics that disrupt key regulatory processes. Such chemicals may lead to the development of new pesticides that provide cost-effective and strategic reductions in mosquito populations and lessen their nuisance and ability to transmit pathogens.